Conventionally, a known technique for a combustion system having an internal combustion engine is multistage injection to inject a fuel into a combustion chamber for multiple times in one combustion cycle. In Patent Literature 1, for example, a good diffusion combustion of a main injection executed after a pilot injection can be achieved by controlling an injection amount and the like and by using the pilot injection in a multistage injection as a target. In the above configuration, a pilot injection amount is set by using a latent heat of vaporization of the fuel that remarkably differs. For example, the pilot injection amount increases in accordance with an increase in latent heat of vaporization of the fuel.